The present invention relates to a semiconductor device and a method of manufacturing the same, in particular, relates to a semiconductor device having a plurality of MIS (Metal Insulator Semiconductor) transistors with the threshold voltages different from one another, and a method of manufacturing the same.
As the film thickness of a gate insulating film is reduced in order to cope with the miniaturization of a semiconductor device, the leak current of the gate insulating film becomes a problem. In order to cope with this problem, the introduction of a high-k film as a gate insulating film material is discussed. As to the introduction, a pinning phenomenon of a threshold voltage of a MIS transistor can be a problem. In order to cope with this, according to, for example, Japanese Patent Laid-Open No. 2007-329237 (Patent Document 1), an Al-based insulating film is inserted into the interface between an Hf-based high-k film and a gate electrode.
Further, according to, for example, Japanese Patent Laid-Open No. 2006-13092 (Patent Document 2), the impurity concentration in a channel region of a MIS transistor is adjusted in order to control the threshold voltage of the MIS transistor having a high-k film.